When driving a long distance road trip you should take a break at minimum every 2 hours.
But ideally you should really stop for a break after an hour or hour and 30 minutes of driving and get out and stretch and walk around for at least 10 to 15 minutes.
It's also a good idea to stop for a restroom break just in case you get somewhere on the road and there's no restroom in sight.
So stop at the first opportunity to use the restroom.
If you don't want to stop after 1 hour and 30 minutes you should always stop for a break after 2 hours of driving and if you have kids along with you that are potty trained and not in diapers then you should stop after an hour or so or when the kid says they need to use the restroom.
Of course if your child or children are still in diapers then they won't need to stop to use the restroom because they would be using the diapers to pee or poop in anyway.
But stop after every few hours to check diapers and change them if you have kids in diapers.
When I had kids in diapers I would stop every 2 hours to change the diapers because I didn't want them sitting in a wet diaper for too long.
Now that my kids are potty trained we stop whenever they need to use the restroom or whenever I need to use the restroom.
When my kids say they need to use the restroom I stop when possible and let them go to the restroom.